The present invention relates to lamp construction and more particularly to an improved lamp construction having a plurality of light-emitting diodes (LEDs) mounted circumferentially about opposed rounded surfaces at the head of the lamp so that light from the LEDs may be projected radially therefrom in substantially all directions.
As illumination sources, LED lamps have long been proposed as an improved substitute for small-sized incandescent lamps because of the LED's superior reliability, rated life and lower power consumption. Various LED lamps have therefore been designed and have effectively replaced small incandescent pilot lamps used as indicator lights on display panels and in various electronic equipment. Examples of such LED lamps are described in U.S. Pat. Nos. 4,211,955, 4,727,289 and 5,160,200.
Existing LED lamp designs have not, however, been as effective in generating brighter amounts of illumination for longer-range signaling purposes, such as those lights used in highway traffic signals and at railroad crossings. Since such signaling lights are required to be readily visible to observers throughout a wide range of viewing angles, they must generate not only a strong beam but one that is substantially uniform over a wide pattern of illumination. Producing a sufficiently bright and uniform beam of illumination has been difficult to achieve using LEDs because of the unidirectional feature of their light emissions that is further characterized by a significant reduction in luminous intensity when observed at angles displaced slightly from the optical-centerline of the LED. While various designs have been developed for grouping LEDs to increase the strength of their illumination, such designs have not addressed the characteristic limited range of luminous intensity exhibited by the LEDs in such a manner that allows LEDs to be used in wide ranging signal light applications.